Add sagemaker option to IntelliChat UI

Intellinode provides a chatbot with Sagemaker llama backend as described in [this wiki](https://github.com/intelligentnode/IntelliNode/wiki/ChatBot#aws-sagemaker-integration).

The required work to update the UI with Sagemaker is as follows:

- Add Sagemaker option in the dropbox.
- Display a drop-down list with one selection: llama.
- Display a textbox with url title.

The backend:
When they send a message with SageMaker selection, call the relevant module from intellinode.

Start with the existing provider-selection UI and message-send entry point, then read the linked AWS SageMaker integration wiki and locate the relevant IntelliNode module. Done means SageMaker appears as an option with a llama selector and URL field, and sending a message with that selection calls the SageMaker backend.

Scritto dal modello di indicizzazione a partire dal testo della issue.